Cardinality in a paraconsistent and paracomplete set theory

This paper develops a rich theory of cardinality in the paraconsistent and paracomplete set theory $\mathrm{B}\mathrm{Z}\mathrm{F}\mathrm{C}$, where sets can be inconsistent ($A$ such that $x\in A$'' is both true and false for some $x$) or incomplete ($A$ such that $x\in A$’’ is neither true nor false for some $x$). We carefully analyze what it means for two potentially incomplete or inconsistent sets to have ``the same size’', construct the corresponding cardinal numbers, and develop the basic theory of cardinal arithmetic. A surprising result is that the cardinality of any set can be expressed as a linear combination of three fundamental cardinal numbers with classical cardinals as coefficients. In that sense, our cardinal numbers form a three-dimensional space over the usual cardinals, much like how the complex numbers form a two-dimensional space over the reals.